1. Field of the Invention
The present invention relates to a safety auxiliary apparatus for an automatic sliding door assembly for selectively opening and closing a doorway by detection of of an object such as a person within a predetermied search area and, more particularly, to the safety auxiliary apparatus operable to keep the door assembly in an opened position in the event that the object is present on a path of movement of the door assembly and out of the search area.
2. Description of the Prior Art
Where an automatic door assembly is installed at a doorway for movement along a predetermined track, a detecting area is generally defined on respective indoor and outdoor sides of the doorway with respect to the door assembly. A starter sensor for detecting the presence or absence of an object within the detecting area is generally in the form of a mat-type sensor or an ultrasonic or pyroelectric sensor having an output unit that is triggered on by the sensor, when the latter detects an approach of the object within the predetermined detecting area, so that the door assembly can be opened.
On the other hand, a safety auxiliary sensor generally utilizing a beam of light is installed at a location adjacent the predetermined track and between the indoor and outdoor detecting areas. This safety auxiliary sensor generally includes a light emitting element, mounted on one of opposed upright braces or columns defining the doorway, and a light receiving element mounted on the other of the upright braces so that a beam of light emitted from the light emitting element can travel towards the light receiving element across the doorway. The presence of the object above the predetennined track can be detected when the beam traversing from the light emitting element towards the light receiving element is intercepted, that is, when the light receiving element fails to receive the beam from the light emitting element. In the event that the safety auxiliary sensor detects the presence of the object above the predetermined track, the door assembly once moved to the opened position can be retained at the opened position even though the output unit is triggered off.
By way of example, in the event that the person attempting to cross the predetermined track in the doorway stops at the predetermined track, the starter sensor will be switched off because of the absence of the person within the indoor and outdoor detecting areas and, therefore, the safety auxiliary sensor is activated to keep the door assembly in the opened position until the person completely leaves from the predetermined track. By so doing, the possibility is substantially eliminated that the door assembly tending to move to the closed position may collide against the person standing on the predetermined track and/or a person's clothing may be caught between the door and the upright brace or between the doors.
However, according to the prior art, since the safety auxiliary sensor is generally mounted on the upright brace installed on an outdoor side with respect to the doorway, it may often occur that in a snowy country snow piles up on one or both of the light emitting and receiving elements forming respective parts of the safety auxiliary sensor and the door assembly is therefore kept opened. Accordingly, a compromise is that in the snowy country the safety auxiliary sensor is to be installed on the indoor side with respect to the doorway and, in such case, no upright brace is available for installation of the safety auxiliary sensor.
Therefore, when the safety auxiliary sensor is to be installed on the indoor side of the doorway, a stay dedicated to support the safety auxiliary sensor must be erected on the floor on the indoor side of the doorway, resulting in increase of the cost for installation. Moreover, the light receiving element of the safety auxiliary sensor mounted on the stay is exposed to the sight of passengers, resulting in deterioration of the appearance of the entrance to a house or building. In addition, a passenger may collide one or both of the light emitting and receiving elements causing failure of the sensor.
Furthermore, since the light emitting and receiving elements are mounted on the upright brace positioned on the outdoor side with respect to the door assembly so that an optical path between the light emitting and receiving elements can lie parallel to the direction of movement of the door assembly along the track, it is not possible to assuredly detect the presence of the object right on the track. For this reason, in the event that two persons stop above the track to talk, the door assembly may move towards the closed position.
In addition, considering that the safety auxiliary sensor is required to detect passage of a child or a small pet animal such as, for example, a puppy or a kitten across the track, the optical path along which the beam travels from the light emitting element towards the light receiving element is set at a relatively low height level, for example, about 60 cm, above the surface of the doorway. For this reason, if an aged person with bowed back walks slowly to trespass the track in the doorway, there is the possibility that although the upper half of his or her body stays on the track, the lower half of his or her body is unable to intercept the beam, resulting in the door assembly being moved towards the closed position. In order to assuredly avoid this possibility, a plurality of the safety auxiliary sensors must be employed and positioned one above the other, resulting in increase of the cost.
In the meantime, an obstruction detecting system for an automatic door assembly which comprises a light emitting device, a light receiving device and a plurality of reflectors disposed in the doorway formed by confronting end surfaces of the doors is disclosed in the Japanese laid-open Patent Publication No. 6-138253. If the obstruction detecting system referred to above were to be used as a safety auxiliary apparatus for an automatic door assembly, it appears that with the use of a single set of the light emitting and receiving devices a plurality of search lines can be set so as to extend parallel to the track for the door assembly and spaced one above the other in a vertical direction by allowing a beam from the light emitting device to reflect several times before it is received by the light receiving device. Accordingly, not only can an object present on the track for the door assembly be inexpensively detected with no fault, but also the system can be immune from adverse influences which would otherwise brought about by, for example, snow, since they can be installed in the doorway.
However, the Japanese publication referred to above merely discloses the principle in which if the light emitting and receiving devices and the plural reflectors are installed in the doorway, the plural paths along which the beam from the light emitting device travels towards the light receiving device in a generally zig-zag fashion can be obtained. Nothing is disclosed therein about means for installing the system in the automatic door assembly in a manner necessary to solve the previously discussed problems. More specifically, the Japanese publication referred to above is silent as to the position and manner in which the light emitting device is installed in the door assembly, an electric wiring system used for the light emitting and receiving devices, and alignment of optical axes of the light emitting device, light receiving device and reflectors.
Considering that when the door assembly is moved to the opened position, the doorway is open full width, even the slightest misalignment of the optical axes would result in the light receiving device failing to receive the incoming beam and also in reduction in amount of light received by the light receiving element, accompanied by a considerable reduction in detection sensitivity.